Category Archives: sdiy

At last I’ve completed my build. All work fine. I’ve made a ghetto case from some scrap shelves, not the best but I’ll make a better case later or buy a metal case from zthee. Not decided yet. Just needed to hold the TTSH in something to being able to calibrate and play it.

Further testing on the main board (right ). I think I’ve located the problem, one of the 4580 in the Mix-B path is at 14.80v on all it’s pins… Gonna swap that with a new one and see if it changes anything.

To do so i’ve bought a desoldering station so i’m waiting on it to be delivered.

Got my mixing desk back from a long term loan and unfortunately it doesn’t work anymore :/

On power up, there’s plenty of hum coming out of it, flashing input and solo leds, scratchy pots and faders, silent channels, etc….

I guess it’s a power issue, either in the PSU or in the desk itself. Looking at the components, it’s packed with cheap chinese electrolytics capacitors, but apart from those the rest is standard thru-hole resistors, ceramic or mylar caps with NJM 4580 SIP package dual op-amps (still available at mouser).

So my best bet is that some electro caps have rendered their last breath and shorted the rails…

Sounds good so far. Need another prototype as i goofed up a bit but quite happy it worked first time!

Edit 1 :

Final version will have Thru-hole transistors for the expo pair as I can’t get any good tracking with smd trannies. I’m tracking 3 octaves with MMBT3904/MMBT3906, 4 octaves with BC850/BC860. Quite ridiculous.

With a pair of 2N3904/2N3906, i’m getting 8 octaves of tracking (go figure…)

I’ll also change the Pulse Width trimpot to 1 turn as having a 25 turn there is making adjusting more difficult .

Still need to test how it behaves under +/-12V and to check temperature stability.

Finished the prototype for the Polivoks VCF in MOTM format. It includes the mods done by Dave Brown. As i’m unable to find NTE888 here in europe, i’ve used LM4250 in replacement. I had to up the 100R resistor to 110R to work with the 4250 otherwise the filter was stalling when the limit switch was on.